Improved Method for the ASTM Platelet and Leukocyte Assay: Use of Minimal Heparinization in a Screening Test for Hemocompatibility of Blood-Contacting Medical Devices

October 24, 2018

Abstract

Most blood-contacting medical devices must be assessed for potential thrombogenicity prior to regulatory approval. A common assay for screening and qualifying devices involves monitoring the reduction of platelet and leukocyte counts in whole blood exposed to the device. We have validated an improved method for assessing a device’s effect on platelet activation and surface adhesion, offering significant improvement over the current ASTM F2888-13 method which uses blood fully anticoagulated by acidified citrate (known to significantly inhibit platelet responsiveness). Our method uses minimal heparinization (final concentration 1 IU/ml) to optimize the response to commonly used control materials, latex, black rubber, and high-density polyethylene (HPDE). We also have shown the assay’s capacity to appropriately assess a legally marketed comparator device (LMCD) with a documented clinical history. The test materials were prepared for incubation and allowed to remain in contact with the citrated or heparinized blood for ~1 hour at 37° C. A complete blood count (CBC) was performed prior to exposure and at the end of the incubation period and reductions in platelet and leukocyte counts were recorded. Results from citrate-anticoagulated assay showed only a marginal response to the positive control, black rubber. Using heparinized blood, the assay generated a robust response to the positive controls, the “intermediate scoring” controls, and also assessed a legally marketed and approved device as clearly non-thrombogenic. This modification adds robustness and sensitivity to this quick and inexpensive thrombogenicity assay and should be incorporated into the next ASTM standards.